Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
netfilter: flowtable: support IPIP tunnel with direct xmit
The combination of IPIP tunnel with direct xmit, eg. bridge device, breaks because no dst_entry is provided to check the skb headroom and to set the iph->frag_off field. This leads to invalid dst usage and can trigger a crash in the tunnel transmit path.
Fix this by moving dst_cache and dst_cookie out of the runtime union so that they can be shared by neighbour, xfrm, and direct tunnel flows. For FLOW_OFFLOAD_XMIT_DIRECT tuples carrying tunnel metadata, preserve route state in these shared fields and release it through the common dst release path.
Since dst_entry is now available to the three supported xmit modes and dst_release() already deals with NULL dst, remove the xmit type check in nft_flow_dst_release(). Moreover, skip the check if the dst entry is NULL in nf_flow_dst_check() which is now the case for the direct xmit case.
Based on patch from Rein Wei <[email protected]>.
Details
- Affected product:
- Debian 10 ELS
- Affected packages:
- linux @ 4.19.0